Apparatus for polishing thermoplastic articles



D 5, 1939. J. s. REID 2,182,388

APPARATUS FOR POLISHING THERMOPLASTIC ARTICLES Filed Dec. 10, 1936 INVENTOK JAMAE 6. REID {16' ATTORNEY.

Patented Dec. 5, 1939 UNITED STATES APPARATUS FOR POLISHING THERMO- PLASTIC James ARTICLES S. Reid, Shaker Heights, Ohio, assignor,

by mesne assignments, to The Standard Products Company, Port Clinton, Ohio, a corporation of Ohio ApplicationDecember 10, 1936, Serial No. 115,101

5 Claims.

This invention relates generally to a method and apparatus for removing the flash or rib from the surface of articles of molded thermoplastic material and for polishing and finishing this sur- 5 face after the flash has beenremoved.

A portion of the surface of such thermoplastic articles inherently possesses slight ribs or flash of molded material at the parting line of the mold sections and sometimes at the gate and adjacent the ejectors. The formation of such ribs occurs regardless of the precision and care employed in the mating of the separable die elements of the mold.

The present invention is designed to remove l5 this rib and render that portion of the surface as smooth and free from flaws as the remaining surface of the article, and further to polish substantially the entire surface of irregular articles in a single operation.

For the purpose of illustrating the principle and operation of the invention, an apparatus for flnishing and polishing to remove the flash and other irregularities, incident to the molding operation, from the surfaces of steering wheels is disclosed, it being understood that other articles of thermoplastic material or having thermoplastic coatings can be finished equally as efficiently by the same principle.

Prior to this invention, these objectionable ribs on the surfaces of steering wheels were removed and polished by a high speed rotary buffing wheel. As the molded steering wheels were ejected and removed from the mold sections, they were transferred to a polishing operator, who took great care in removing the flash and flnishing the surface of each wheel. Oftentimes the workman would apply too much pressure on the steering wheel and cause the bufling wheel to burn or scorch the thermoplastic coating so as to produce discolorations and blemishes which are as equally objectionable as the ribs. Any such discolorations and blemishes occurring in a highly polished surface are easily and readily detected. In articles having a thin coating of thermoplastic material molded over a preformed core, as in the case of the illustrated steering wheels, extreme care must be taken in the polishing operation so that the surface is not gouged or burned. Thus any steering wheels having such defects resulting from the polishing operation must necessarily be discarded or scrapped with the consequent loss of all time and material in the manufacture of the wheels.

Another objection to the previous method of polishing lies in the fact that it is expensive and slow. Only one wheel at a time can be finished and the quality of the finished surface depends entirely upon the skill of the operator. Thus where a number of polishing operators are em: ployed, the quality of the work turned out by each operator inherently varies and furthermore, the quantity of scrapped articles resulting from careless polishing is relatively high.

An important object, therefore, of the present invention lies in the provision of a method and apparatus for smoothing and polishing the surfaces of articles of thermoplastic material by subjecting the surface to be finished to a, suitable polishing medium or fabric with a constant and uniform pressure and by causing relative movement between the article and the polishing fabric, thereby quickly and efilciently removing the flash and polishing the surface to the desired quality.

An equally important object is to provide such a finishing and polishing method and apparatus which will greatly reduce the time heretofore required for the finishing operation and also decrease the number of articles heretofore damaged and rejected by the hand polishing method.

Another object is to polish non-planar surfaces more efficiently.

Other objects and advantages of the present invention will become apparent from a considera tion of the following description taken in conjunction with the accompanying drawing, wherel Fig. 1 is a longitudinal sectional view through the polishing .device and through the articles to be polished;

Fig. 2 is an end elevation of the device showing the articles about to be inserted therein; and

Fig. 3 is an enlarged fragmentary longitudinal sectional view through the device showing the articles positioned within the polisher.

Referring particularly to Fig. 1, a preferred form of apparatus for effecting the method of polishing the unfinished surfaces of a number of steering wheels I is shown for purposes of illustration and comprises an open ended rigid cylinder 2, the inside diameter of which is somewhat larger than the diameters of the steering wheels. This cylinder may be made of any desired material which is sufficiently rigid to withstand the stresses incident to the operation of the device and is preferably sheet metal or a thin wall casting.

A suitable tubular fabric sleeve, 3, such as canvas or felt is accommodated in coaxial relation in the cylinder 2, the major portion of the peripheral wall of the sleeve being spaced radially 55 inwardly from the inner wall of the cylinder. This fabric liner 3 is shown supported within the cylinder 2 by attaching the extreme end portions 4 of the liner to the corresponding ends of the cylinder. A convenient method of so supporting the liner is by turning back the end portions 4 thereof around the ends of the cylinder so that these portions 4 will lie on the outer surface of the cylinder. While in this position the end portions 4 are firmly clamped to the cylinder 2 by straps 5. r

This liner 3 provides the polishing surface or medium for removing the ribs and finishing the outer periphery of the steering wheels. This polishing surface is held in uniform pressure engagement against the entire outer rim periphery of each wheel by filling the space 6 between the liner 3 and the cylinder 2 with compressed air, the air being conducted to the space through the medium of a suitable pipe I 0. I The material of the liner 3 is preferably such that it may be' inflated and distended by the air, while permitting a slight exfiltration of the air through the peripheral wall thereof. Heavy duck canvas has been found suitable. It will be seen that as air enters the space 6, the liner 3 bulges or distends inwardly radially and the polishing surface thereof yieldably engages the portion of the rim periphery on which the rib or flash is located, as shown in Fig. 3, and partiallyembraces adjacent portions of the rim surface, regardless of the contour. The surface actually embraced depends upon the air pressure and relative size and slackness of the sleeve. Thus the sleeve readily accommodates itself to the surface contour of the article.

A quantity of wheels I are guided into one end of the cylinder 2 by an axial rod I I which extends substantially throughout the entire length of the cylinder 2. For convenience in handling these steering wheels as a unit the entire quantity may be mounted on a length of tubing I2 which slips into the hub of each wheel and which fits over the axial rod I I. Suitable collars I3 are employed for the purpose of retaining the group of Wheels to the tubing I2.

To obtain the best results the group of wheels I so mounted on the tubing I2 should not extend more than half or two-thirds the length of the cylinder 2 so that when the group is pushed entirely within the cylinder an appreciable axial movement of the wheels relative to thepolishing surface is permitted While all of the wheels remain entirely within the confines of the cylin- .der.

While the group of wheels are thus disposed within the cylinder 2, the' tube I2, and consequently the wheels, are caused to reciprocate as a group to and fro axially along the rod II and between the end limits of the cylinder. During this operation the fabric liner 3 frictionally engages the entire outer periphery of each wheel rim with an equal pressure which, as stated above, is caused by the pressure of the air within the space 6. Thus the rib or flash of each wheel is easily and quickly removed and the surface rendered flush and highly polished. Due to the exfiltration of air during the polishing operation a cooling eifect is provided so that undue heating and resultant damage to surface and fabric are prevented. I

In this polishing apparatus there is much less danger of ruining wheels by burning as when a buffing wheel is used. This is due to the fact that the relative speed, at which the surface to be finished moves over the polishing fabric, is necessarily much slower. Furthermore, the unit pressure of the fabric on the surface is relatively low and uniformly distributed around the wheel periphery, whereas in the hand-bufiing method the unit pressure is high, variable, and concentrated at a limited zone.

Since the air pressure in the space 6 is constant, it follows that the pressure of the polishing fabric against the rim peripheries of all the wheels is uniform and constant. This pressure is maintained at a magnitude suflicient to accomplish the best results in the least amount of time, and may be varied to change the rapidity of polishing and amount of surface engaged.

If it is desired to engage only the flash or rib of the article, the initial longitudinal tension of the liner 3 may be increased so that the portion of the liner embracing the rim periphery contacts only a limited surface. Thus, as the initial tension on the linear is increased the magnitude of the engaging surface is correspondingly reduced.

The cylinder 2 may be mounted for oscillation about its axis during the to and fro movement of the wheels within the cylinder. Thus, in one cycle of inward and outward movement of the group of wheels the cylinder may be caused to rotate in one direction a limited degree and during the next cycle of inward and outward movement the cylinder may be rotated in the opposite direction the same or a different amount. Such a compound relative movement will facilitate the finishing and polishing operation and prevent concentration of wear on the line.

The inner peripheries of therims also possess the characteristic flash of thermoplastic material at the parting line of the mold. This flash must likewise be removed and the surface polished flush before the wheel is ready for use. For this purpose I use a number of long, narrow, pneumatically inflated fingers I5 which are made of fabric material similar to the fabric liner 3. These inflated fingers each pass between adjacent spokes of the steering wheels so that the polishing surface thereof engages the inner rim periphery of each Wheel. These fingers I5 are preferably mounted on a separate plate I6 independent of the cylinder 2 and extend substantially the entire length of the cylinder.

Each finger I5 is supported in a position parallel to the axis of the cylinder 2 by a suitable rod I! which is secured at one end to the plate I6. The other end of the rod is attachedto and supports the free end of the finger I5, as shown in Fig. 1. This attachment may be made in any convenient manner as by suitable washers 20 and lock nuts 2|.

The free end of each finger is pneumatically closed and the opposite or open end is sealed against the surface of the plate I6 by a clamping ring 23. Thus, any air under pressure admitted into the fingers through pipes 25 is confined and reacts outwardly against the walls of the fabric to cause a definite and uniform pressure engagement of the polishing surface against the inner rim peripheries of the wheels.

The cross sectional shape of each finger I5 is preferably substantially similar to the space defined by adjacent spokes and the intermediate section of the steering wheel rim so that upon inflation of the fingers the outer or polishing surfaces thereof contact and fit the surfaces of the steering wheel to be polished with the same amount of pressure.

4 The material from which the liner 3 and the fingers l5 are made may be, as stated above, canvas or felt. If desired to maintain a relatively high air pressure within the space 6 and within the confines of the fingers I5, the fabric material may be impregnated with a suitable rubber composition which will partially or fully seal the pores in the fabric and prevent rapid escape of air.

From the above description it will be seen that a polishing method and apparatus has been provided which is capable of finishing the surfaces of molded steering wheels or other non-planar surfaces in a much more satisfactory manner and in much less time than has heretofore been possible. The air pressure which causes the polishing surfaces of the liner and fingers to contact the surfaces of the steering wheel can be controlled and maintained to insure the proper engaging and polishing pressure and thereby easily and quickly produce a uniform quality of surface at all times.

Having thus described my invention, I claim:

1. An apparatus for smoothing and polishing a portion of the surface of an article, said apparatus comprising a tubular member of sufficient size to receive and accommodate the article in coaxial relation therein, a fabric liner attached only at its ends to the ends of the tubular member and having its peripheral wall spaced radially inwardly from the tubular member, the fabric liner having an inwardly exposed flexible article engaging and polishing surface engageable con currently with the entire peripheral surface of the article, means for guiding the article for movement within and relative to the tubing and liner, and means for producing a uniform yielding pressure engagement of the polishing surface of the liner against the said portion of the surface of the article, whereby upon movement of the article relative to the polishing surface of the liner, the said portion of the surface of the article is rendered flush and smooth.

2. An apparatus for polishing a portion of the surface of an article comprising a cylindrical supporting member, a liner of fabric secured at its ends only to the ends of the supporting member and spaced radially inwardly from the inner wall of the member and having a flexible article engaging surface, means by which fluid can be introduced into and maintained under pressure within the space between the liner and the member for holding the liner with the flexible surface in yieldable uniform engagement with the entire peripheral surface of the article, and means by which relative movement of the liner and article can be eifected.

3. An apparatus for smoothing and polishing the unfinished outer peripheral portion of the surface of an annular article, comprising an inflatable yieldable member having a universally yieldable article engaging and polishing surface concurrently engageable with the entire outer peripheral portion of the annular article, said inflatable member being unrestrained throughout the entire article-engaging surface, means for supporting and guiding the article for move-v ment relative to the member, and means enabling inflation of the member with fluid for producing uniform pressure engagement of the polishing surface of the member with the unfinished portion of the surface of the article.

4. An apparatus for smoothing and polishing the unfinished outer peripheral portion of the surface of an annular article comprising an infiatable yieldable fabric sleeve member having a yieldable article engaging and polishing surface portion, means supporting the said articleengaging surface portion entirely beyond the limits thereof, means for supporting and guiding the article within the sleeve member for coaxial movement relative to the member, said inflatable member being capable of receiving fluid under pressure for producing uniform pressure engagement of the polishing surface of the member with the entire unfinished outer peripheral portion of the surface of the article.

5. An apparatus for concurrently polishing the inner and outer peripheries of a steering wheel rim annulus comprising a cylindrical member, a tubular fabric liner attached at its ends to the ends of the cylinder and spaced from the inner wall of the cylindrical member, said liner being engageable with the outer periphery of the rim, fabric fingers extending inwardly and longitudinally of the cylinder, and engageable with the inner periphery of the rim, means for guiding the wheel for reciprocable movement axially of the cylinder while the liner and fingers are so engaged with the annulus, and means enabling inflation of the liner and fingers with fluid to cause uniform pressure engagement of the outer and inner peripheries of the rim, respectively, during the axial reciprocation of the wheel relative to the liner and fingers.

JAMES S. REID. 

